Automotive 6 Volt Generator Transistor Voltage Regulator

[Danwvw]

I have moved ahead with the new ideas for this type of DYNAMO voltage regulator, This new redesign of Prototype One will use the LM393 Dual Comparator IC so only one IC is needed. Also the LM393 while not being quite as heat tolerant begins to Operate at Just 2 volts. However start up is not a problem with the previous design either.

 

[Danwvw]

LM393 Comparator ?
The above circuit does not work! The LM393 Comparator doesn't seem to have the current carrying ability that the LM311P has. When Pin 7 is pulled up with a resistor value of 300 ohms it sinks at about 1.5 volts however it effects pin 1 which then won't sink below about 6 volts with its 1.2k pullup. This was with VCC 8 volts.
Do I have something wrong or is this a design feature of the LM393?

 

[rjenkinsgb]

It's very different, from a look at both data sheets.

The LM311 is rated to sink 50mA while the 393 has a guaranteed minimum sink of just 6mA and 15mA typical, with saturation voltage ratings only given for less than 4mA..

 

[Danwvw]

Yes, Thanks for the Heads up on that, I did notice it's curves saturate just above 10ma, If it will work with a transistor I might go ahead with it though but really what I need is a different IC with the same pin configuration as the LM393 but With LM311P Current Sink's?
LM393

Idea:

 

[KeepItSimpleStupid]

Would re-designing based on the LT6700 or LT6700HV be of any help? https://www.analog.com/en/products/lt6700.html#product-documentation

There is a single comparitor version of this chip too. You get a reference as well and it'a automotive qualified.

 

[Danwvw]

Thanks "KeepitSimpleStupid" Unfortunately the Voltage Ref is common in this kind of IC and also it has similar current limits to the LM393, I tried the transistor I think I fried something. I did some Comparator research yesterday and didn't find any. But as your Avatar Name implies, I would love Ideas on how to further simplify the design. Thanks and Merry Christmas,

 

[KeepItSimpleStupid]

I don;t understand what your trying to say. That IC essentially lets you set a switching point < 400 mV or > 400 mV intrinsically. If you want a switching point of 6V say, you divide 6V down to 400 mV.

it's just wacky that you need a different IC for reference to both inverting inputs. reference to both non-inverting inputs and one to the inverting and non-inverting input.

 

[Danwvw]

Thanks, I would need to study it more to understand what you're saying about switching.. But the LT6700 does not have a independent comparator from its internal voltage reference. An independent comparator is needed to monitor both sides of the generator output "Shunt" for current monitoring.
I got some new graphing paper for Christmas so have been figuring out another solution that uses the LM393 and a LT431 Programmable Precision Voltage Reference to Drive the Voltage Regulator.

 

[Danwvw]

I Got it working with the 2N2222 as a Driver, Had a few mistakes, opens and shorts and I burned out a Diode.

 

[Danwvw]

With LM393 and 2N2222A Driver:
01/23/2021 Update: This LM393 with the 2N222A has been in the car now for a few days and I am starting to get a feel for it. It's A little different. Excellent at starting charging. A little, about 1/4 of a Volt Output Voltage variance seems to be going on with it intermittently. I keep turning it down then it. will jump up again, today it jumped up then back. down after driving around awhile. Could be the Voltage Potentiometer however given the history of these new 10 turn Potentiometers like this one has on the current that probably is the cause, have ones like the 1st current potentiometers I got on order and will replace it when they come in. Also I should change my elcheapo voltage display in the car, sometimes it jumps down to 3 and a half volts and gets dim but it's always been Flakey and I know it's not the source of the 1/4 volt increase as the 1/4 volt increase sets off the over voltage alarm.

 

[Danwvw]

Testing on the Bench:

 

[Danwvw]

Would re-designing based on the LT6700 or LT6700HV be of any help? https://www.analog.com/en/products/lt6700.html#product-documentation

There is a single comparitor version of this chip too. You get a reference as well and it'a automotive qualified.

Here is a pretty simple Design that might work with the LT6700 Comparator, What I like about it is, only 3 components would be mounted on the circuit board, and its regulation voltage could be fixed. There isn't any current regulation but a 50 amp fuse could be used for protection. I would have to see how much current it draws with the key off, perhaps it would be acceptable like other commercially available 6 volt electronic dynamo voltage regulators which run off the battery. Just need to get my hands on the LT6700 #1 or #2 etc... and a few other components.
January 4, 2021 LT6700 Design Idea:

 

[KeepItSimpleStupid]

~100K resistor gate to ground

How about working with https://www.rockauto.com/en/moreinfo.php?pk=6309246&cc=3444592&jsn=447 battery current sensor. It snaps around the battery cable on newer vehicles. Orientaion matters.

GM Charging system problems: Understanding the EPMS system

GM charging system problems? Learn how the GM EPMS power management system works and how to diagnose and fix charging issues

ricksfreeautorepairadvice.com

You can buy PWM to voltage modules. I'll look when I get a chance.

LT1431 for the zener's https://www.analog.com/media/en/technical-documentation/data-sheets/1431fe.pdf

Your gonna hate me, right?

 

[KeepItSimpleStupid]

I think you missed the point of the comparitor. Use this calculator: https://ricksfreeautorepairadvice.com/gm-charging-system-problems/

use, 6, 4, E96, 10000 and get 140K and 100K, No external reference needed. You divide the desired voltage of 6 to 400 mV.ag

6V * 140K *(0.4V)* 100K * GND (I think I did it right)

 

[Danwvw]

You lost me just past 100K Gate to Gnd!

 

[KeepItSimpleStupid]

You lost me just past 100K Gate to Gnd!

Nearly anytime you use a FET in a slow speed design, you need to do two things:
1. Have a place for the gate leakage current to go, otherwise the FET turns on accidentally (e..g. Open gate), it's a really small current.
2. Put a 100-240 ohm resistor in series with the gate, Why? There is gate capacitance to charge and the voltage across a capacitor can't change instantaneously.

High speed circuits with gate drivers can force a lot of current for a short time into the gate capacitance and suck the charge out of the gate.


The comparitor non-sense. Using 400 mV allows you to compare at any arbitrary voltage > 400 mV. You just bring the higher voltage down to the 400 mV level. You can use high valued resistor dividers to do so.

ASIDE: https://en.wikipedia.org/wiki/E_series_of_preferred_numbers

 

[KeepItSimpleStupid]

You lost me just past 100K Gate to Gnd!

Nearly anytime you use a FET in a slow speed design, you need to do two things:
1. Have a place for the gate leakage current to go, otherwise the FET turns on accidentally (e..g. Open gate), it's a really small current.
2. Put a 100-240 ohm resistor in series with the gate, Why? There is gate capacitance to charge and the voltage across a capacitor can't change instantaneously.

High speed circuits with gate drivers can force a lot of current for a short time into the gate capacitance and suck the charge out of the gate.


The comparitor non-sense. Using 400 mV allows you to compare at any arbitrary voltage > 400 mV. You just bring the higher voltage down to the 400 mV level. You can use high valued resistor dividers to do so.

ASIDE: https://en.wikipedia.org/wiki/E_series_of_preferred_numbers

 

[KeepItSimpleStupid]

You could take away gate drive if the battery voltage is low, so that the alternator is off when starting.

In the old cars, i think it was done as part of the incadesent charging indicator.

What triggers a "Generator" warning light

My CTLS has two warning lights on the panel, one marked "Engine", and the other "Generator". From the wiring schematic, the "Engine" light appears to be triggered by whatever events the Dynon 120 EMS deems worthy of frightening the pilot's wife. But the "Generator" light is just wired to the "L" ...

ctflier.com

 

[Danwvw]

I have ordered a couple LT6700's I wanted see what can be eliminated, I have a scope and can check for oscillation or wave forms that aren't square, I tell you though the LM393 circuit test out I have had it on the scope, it doesn't oscillate. The LM311P also above being tested in the car is working flawless (Failed Jan 16 due to a bad 10K pot!) but it has a gate circuit like your talking about. Yes the Bosch Alternators like some I have had on VW air Cooled and even later Porsche Water Cooled depend on the Alt Indicator lamp current to start charging. Bosch Generators Don't. But the Gen Indicator lamp is between D+ (ie gen output) and the key on 12 volts. Much like the Alternators. Thanks.

 

[KeepItSimpleStupid]

The LM311 is a very early comparitor.

There is a single version of the LT6700..https://www.analog.com/en/products/lt6703.html#

I had a couple of failures that were unique:

Car just died with a dead battery. The rotor solder joint failed. So an open rotor. The idiot light never saw it.
It was the same vehicle, but I did have corrosion on the bulkhead connector. Problem may have been related.
It was nice when the alternators were rebuildable. Toyota were if you had a spot welder. GM with their drop-in internal regulator wasn't
bad. A 1960's Chrysler had brushes going from the rear housing and along the shaft.

I do think it's wise to make sure the rotor is off when starting the vehicle.

This https://m.littelfuse.com/~/media/el...utomotive_tvs_diodes_application_note.pdf.pdf is worth looking at.